1. Field of the Invention
This invention relates to a liquid jet recording head, and in particular to a liquid jet recording head in which the temperature of the recording liquid is controlled, whereby the concentration of recorded images can be adjusted relative to various kinds of plain paper.
2. Related Background Art
Liquid jet recording methods can accomplish high-speed recording in which noise produced during recording are negligible, and moreover have recently been drawing attention in that they can accomplish recording without requiring any special processing such as fixation on so-called plain paper.
Among such methods, the liquid jet recording method described, for example, in Japanese Laid-Open Patent Application No. 54-51837 or German Laid-Open Patent Application (DOLS) No. 2843064 has features differing from those of the other liquid jet recording methods in that heat energy is caused to act on liquid to obtain a driving force for discharging liquid droplets.
That is, this liquid jet recording method is such that liquid subjected to the action of heat energy undergoes a state change accompanied by a steep increase in volume and the recording liquid is discharged from a discharge port at the fore end of a recording head unit by an action force based on the state change, whereby flying droplets are formed and adhere as dots to a recording medium to thereby accomplish recording. The the liquid jet recording method disclosed in DOLS No. 2843064 has the feature that not only it is very effectively applied to the so-called drop-on demand recording method, but also it can easily embody a recording head of the full line type having multiple orifices at a high density and therefore can provide images of high resolution and high quality at a high speed.
FIG. 7 of the accompanying drawings shows an example of the liquid jet recording head according to the prior art. In FIG. 7, the reference numeral 1 designates the substrate portion of the recording head, the reference numeral 2 denotes liquid paths formed in parallel on the substrate portion 1, the reference numeral 3 designates a common liquid chamber connected to the liquid paths 2, and the reference numeral 4 denotes heat-acting portions disposed in the liquid paths 2. Electro-thermal converting members as heat energy generating means for causing recording liquid to the discharged as flying liquid droplets from discharge ports 5 are provided in the heat-acting portions 4. Each electro-thermal converting member has a pair of electrodes and a heat generating resistance layer connected to these electrodes for generating heat, although they are not shown. The reference numeral 6 designates an upper lid member, and the reference numeral 7 denotes a recording liquid supply port formed in the upper lid member 6 over the common liquid chamber 3. Recording liquid is supplied from an outside recording liquid tank to the common liquid chamber 3 by a tube or the like through the supply port 7.
In such a liquid jet recording head, the recording liquid directed from the common liquid chamber 3 to the liquid paths 2 is heated and vaporized by the electro-thermal converting members in the heat-acting portions 4 being electrically energized, and a variation in the pressure thereof causes the recording liquid to be discharged as liquid droplets from the discharge ports 5 and shot onto a recording medium to form dots, and an image is recorded by an aggregate of these dots.
However, the prior-art liquid jet recording head as described above has suffered from the drawback that the diameter of liquid droplets discharged is fixed due to the limitations or the like in the manufacture of the head while, on the other hand, the rate of blur (the diameter of dots/the diameter of discharged liquid droplets) differs depending on the kinds of recording medium and accordingly, the recording concentration becomes diverse depending on the kinds of recording medium, but nevertheless, in the formation of discharged liquid droplets, no special consideration has been given to the speed thereof and the temperature of the recording liquid.